Rubber product.



HARRY BAlEtRINGrER COX, OF BEJDFORD HILLS, NEW YORK.

'.IR|UIBBER PRODUCT.

No Drawing. Original application filed. July 29, 1914.

7 new and useful Itubber Product, of which the following is a divisionofmy former ap plication, filed January 16, 1913, Serial No. 742,402.

The methods now in use for the recovery of rubber stock from oldvulcanized rubber generally involve the subjection of the-rubber undervarious conditions of heat, with or without pressure, to aqueoussolutions of one kind or another. These processes not merely injure thegum itself, but also affect to a very substantial extent the substanceswith which it is compounded, so that the resulting stock is very muchinferior to the'original stock and differs from it substantially withrespect to many of its elements. Said processes moreover are cumbersome,laborious and expensive.

I have discovered a process whereby the stock produced is maintained inclose approximation to the original stock retaining the originalqualities of the gum approximately unimpaired, and also the originalcompounds so far as their usefulness is concerned. My process moreoveris neither cumbersome, laborious nor expensive.

Although I do not Wish to be understood as limiting myself to theattainment of all of the above results, or to the most perfect form ofmy process, I will now proceed to describe the process as I at presentprefer to carry it out. I first prepare what I will herein refer toasmy. resin solution, which I believe to be new per se, and which. Iprefer to prepare as follows: I purify commercial resin by heating ituntil it boils and continuing the boiling until I evaporate thecontained water and other volatile sub stances. .This boiling lastsabout two hours and is continued until the resin stops foam-- ing. Ithen permit the resin to cool and grind it to a fine powder. Anycommercial resin may be employed although I preferably employ rubberresin. I next dissolve the resin at ordinary temperature in gasolene andallow the insoluble parts of the resin to settle and decant off thesolution. I may use two pounds of the purified resin to 100 pounds ofgasolene, where the resin solution is to be employed for the treatmentof auto- Specification of Letters Patent. Pg t gnflg edl 3113, 241,,19116,

filed January 16, 1913, Serial No. 742,402. Divided and this applicationSerial No. 853,804.

mobile tire tread stock. For lower grades of stock a higher percentageof resin to the gasolene is preferable-sometimes as high as 4%. Forhigher grades of stock the percentage of resin will be lowersometimes aslow as 1%. v

The resin solution is very much less volatile than is gasolene withoutthe resin.

I grind the rubber'stock to be treated to about the fineness of coarsesand to facilitate absorption of the resin solution. I put the stock inan open tray and pour over it sufiicient resin solution.

In determining the amount of resin solution to be used for a givenquantity of vulcanized stock I calculate the amount of resin that Ibelieve to be necessary to replenish the stock with the freed resin thathas been affected by vulcanization, and employ an amount of resinsolution containing this'calculated amount of resin. I have found inpractice thata proportion of about 3 pounds of resin to over 100 poundsof ground automobile tire tread stock will answer the purpose.

As the resin solution is absorbed the stock will swell say from two tofour times its bulk, depending upon the quality of the stock, and alsoupon the amount of gasolene employed as the vehicle for carrying theresin into the stock. I let the mass stand preferably until it hasstopped swelling, which may take about an hour. I next heat gently anduniformly until the mass becomes tacky. For this purpose I prefer a heatabout from 190 to 200 F. for about from four to twenty hours, dependingupon the quality of the stock. The greater the mineral'matter in thestock the less time is required. Or the lengthof time of this heatingmay be lessened to about one hour by subjecting the mass to live steamof about twenty poundspressure. This reduction in time is, however, atthe expense of a somewhat lower .quality of product because of theincreased heat. In this step, length of time is more or less asubstitute for heat so that the operation might take place at ordinarytemperature in about from tento fifteen days. I next remove thegasolenefrom the mass either by distillation, by vacuum extraction, orby live steam. I next dry the stock, if necessary, and it is then incondition to be milled. v

The recovered stock thusproduced differs from the present ordinarydevulcanized stock in the following respect: The tensile strength ofpresent ordinary devulcanized rubber I understand to be less than of theoriginal, whereas the tensile strength of my product is above 50% andmay be as high as of the original.

The stock is characterized by ease and rapidity of milling. The gum isapproximately unimpaired. The mineral compounds remain to such'an extentthat the stock does not have to be recompounded. Even though certain ofthe mineral compounds, as for example the .litharge, have been changedby the-original vulcanization they still may retain their efliciency asfillers in their changed form.

Compared with original unvulcanized stock, my stock differs in not beingsoluble in gasolene, Whereas original. unvulcanized stock is solubletherein. Moreover by application of heat my stock may be reduced to aliquid solution in said resin solution, whereas under similar conditionsoriginal unvulcanized stock is reduced to a viscous consistency.

My theory of the operation which takes place in the above process is asfollows: During the process of vulcanization it appears that there is achange in the constitution of the resin or a more or less completevolatilization thereof, and that the above process replenishes the gumwith resin to take the place of that so changed or volatilized in thevulcanization. This replenished resin may in turn be changed, etc., byrevulcanization and again replenished, and this replenishment .andrevulcanization may occur as many times as it is desired to rework theproduct.

Whatever kind of resin I employ in making my resin solution, I mayimprove said solution by adding thereto a small percentage of vulcanizedgum stock which has been reduced to a liquid by the resin solution andheat as above described. The addition of rubber resin to stock which hasbeen partially or in whole deprived of its original content of rubberresin serves practically to reduplicate the original unvulcanized'rubmay be used over again in subsequent operations of my process.

I do not wish to be understood as limiting myself to gasolene as'acarrier medium for the resin to the exclusion of other carrier mediumsfor resin- I may use naphtha or kerosene as a carrier medium for theresin.

In case the old vulcanized rubber to be treated is combined with fiber,I remove the fiber preliminarily in my treatment of the rubber.

Having produced my recovered stock as aforesaid and milled the same, Imay prepare it for revulcanization by mixing it with the calculatedamount of sulfur necessary to combine with the amount of resin withwhich I have replenished it by my said process.

The approximation of my recovered stock to the original is such that itis revulcanizable in the same time and temperature as that taken in theoriginal vulcanization. Therefore, a factory employing my process maywith impunity mix its recovered stock with its new stock because both ofthem are adapted to the same time and temperature of vulcanization,therefore the conditions which properly vulcanize one would properlyval-- canize the other when the two are mixed.

What I claim and desire to secure by Letters Patent of the United Statesis 1. A product comprising recovered rubber stock replenished withrubber resin.

2. A product comprising recovered rubber stock replenished with resin,and a material obtained by dissolving vulcanized gum in rubber resin.

In testimony whereof I have hereunto signed my name in the presence oftwo subscribing witnesses.

